MPP, Sendust,
Kool Mu, High Flux are part of the powder core family and are similar
to Iron Powder cores. They are used as inductor, choke and filters. The
choice of one type of powder material over another often depends on the
following:

1) DC Bias
Current through the inductor
2) Ambient Operating Temperature and acceptable temperature rise. Ambient
temperature of over 100 deg C is now quite common.
3) Size constraint and mounting methods ( through hole or surface mount
)
4) Costs : iron Powder being the cheapest and MPP, the most expansive.
5) Electrical stability of the core with temperature changes
6) Availability of the core material.
With powder cores, high permeability material is ground or atomized into
powder. The permeability of the cores will depend on the particle size
and density of the high permeability materials. Adjustment of the particle
size and density of this material leads to different permeability of the
cores. The smaller the particle size, the lower the permeability and better
DC bias characteristics, but at a higher cost. The individual powder particles
are insulated from one another, allowing the cores to have inherently
distributed air gaps for energy storage in an inductor.

This distributed air gap property ensures that the energy are stored evenly
through the core. This makes the core have a better temperature stability.

MPP cores has the lowest overall core loss and best temperature stability.
Typically, inductance variance is under 1% up to 140 deg C. MPP cores
are available in initial permeabilities (µi) of 26, 60, 125, 160,
173, 200, and 550. MPP offers high resistivity, low hysteresis and eddy
current losses, and very good inductance stability under DC bias and AC
conditions. Under AC excitation, inductance change is under 2% (very stable)
for µi=125 cores at AC flux density of over 2000 gauss. It does not
saturate easily at high DC magnetization or DC bias condition.The saturation
flux density of MPP core is approximately 8000 gauss ( 800 mT)

High Flux cores is composed of compacted 50% nickel and 50% iron alloy
powder. The base material is similar to the regular nickel iron lamination
in tape wound cores. High Flux cores have higher energy storage capabilities,
and higher saturation flux density. Their saturation flux density is around
15,000 gauss ( 1500 MT), about the same as iron powder cores. High Flux
cores offers slightly lower core loss than Sendust. However, High Flux's
core loss is quite a bit higher than MPP cores. High Flux cores are most
commonly used in application where the DC bias current is high. However,
it is not as readily available as MPP or Sendust, and are limited in its
permeability choices or size selections.

Applications
:1) In Line Noise filters where the inductor must support large AC
voltages without saturation.
2) Switching Regulators Inductors to handle large amount of DC bias current
3) Pulse Transformers and Flyback Transformers as its residual flux density
is near to zero gauss. With the saturation flux density of 15K gauss,
the usable flux density ( from zero to 15K gauss) is ideally suited for
unipolar drive applications such as pulse transformer and flyback transformers.

SENDUST
Composition: Al-Si-Fe
Sendust Powdered Cores (also known as Koolmu Cores) with its distributed
air gap are made from a ferrous alloy powder. The base material is approximately
85% iron, 6% aluminum and 9% silicon. Sendust powders are made by atomization
the base alloy melt. The powders are insulated and then pressed into various
core shapes (toroidal or E-Cores) under very high pressure.

Sendust cores
have very low core loss and good temperature stability. In high frequency
applications, sendust cores offer up to 80% reduction in core loss over
iron powder cores. Hence, Sendust cores significantly lower the temperature
rise. Sendust cores also exhibits very low magnetostriction coefficient,
and it is therefore suitable for applications requiring low audible noise.
Sendust cores has a saturation flux density of 10,000 gauss.

Sendust cores are available in initial permeabilities (Ui) of 60 and 125.
Sendust core offer minimal change in permeability or inductance (under
3% for ui=125) under AC excitation. Temperature stability is very good
at the high end. Inductance change is less than 3% from ambient to 125
deg C. However, as the temperature decreases to 65 deg C, its inductance
decreases by about 15% for µi=125. Also note that as temperature
increases, sendust exhibits a decrease in inductance versus an increase
in inductance for all the other powder materials. This could be a good
choice for temperature compensation, when used with other materials in
a composite core structure.

Sendust cores cost less than MPPs or high fluxes, but slightly more expensive
than iron powder cores. For application involving DC bias conditions,
use the following guidelines. To get under 20% decrease in initial permeability
under DC bias condition:

Switching
Regulator Inductors: Sendust Cores are well-suited for high energy
storage/filter inductors used in switch mode power supplies. The 10,000
gauss saturation level of sendust cores provides a higher energy storage
capability than standard MPP cores or a gapped ferrite cores of the
same size and permeability. Sendust cores are a better choice than powdered
iron if there are significant ripples to be filtered. However, Sendust
Cores are a little more expensive than iron powder cores.

In-Line
Noise Filters: Sendust cores are ideal for in-line noise filters
where the inductor must support large ac voltage without core saturation
occurring. Line filters using Sendust cores can be smaller in size,
requiring fewer turns than by using ferrite cores.

They are available in many popular sizes and permeabilities ranging from
60 to 125 Ái. Also, Sendust E-cores are available in AL value
ranging from 10 nH/N2 to 210 NH/N2 with core sizes
with inside diameter ranging from 0.110/2.79 mm to .785/19.94 mm and outside
diameter ranging from 0.500/12.7 mm to 3.0/77.5 mm. Please check with
factory for other sizes and permeabilities here.

Core
FinishThe MPP, Sendust and High Flux cores are uniformly coated with
a special epoxy finish. This finish provides a tough chemical resistance
and high dielectric protection for the cores.